A robot hand includes a plurality of finger mechanisms configured such that fingertip portions thereof get close to each other and separate from each other. The robot hand can hold a work by reducing a mutual interval between the fingertip portions. As disclosed in PTL 1, examples of a conventional finger mechanism are a simple rotary type, a parallel link type, and a linear type.
A simple rotary type finger mechanism 900 shown in FIG. 9A includes a pair of swinging links 911, each having a base end portion pivotally supported by a base 901. Tip end portions of the swinging links 911 are fingertip portions 915. When the swinging links 911 swing by motors, not shown, the mutual interval between the fingertip portions 915 changes.
A parallel link type finger mechanism 920 shown in FIG. 9B includes driving links 931 and driven links 932, each having a base end portion pivotally supported by a base 921. Tip end portions of the driving links 931 and driven links 932 are pivotally supported by holding members 933. The driven link 932 extends in parallel with the driving link 931. The holding members 933 are fingertip portions 935. When the driving links 931 swing by motors not shown, the driven links 932 also swing, and this changes the mutual interval between the fingertip portions 935.
A linear type finger mechanism 940 shown in FIG. 9C includes a ball screw 951 having one end portion at which a right-hand thread is formed and the other end portion at which a left-hand thread is formed. A pair of linearly moving links 952 are threadedly engaged with respective end portions of the ball screw 951 so as not to be rotatable. Tip end portions of the linearly moving links 952 are fingertip portions 955. The ball screw 951 is rotatably supported by bearings 942 provided at a base 941 and is coupled via a coupling member 943 to a motor 944 attached to an outer surface of the base 941. When the ball screw 951 is rotated by the motor 944, the linearly moving links 952 linearly move on the ball screw 951, and this changes the mutual interval between the fingertip portions 955.